/*
 * call-seq:
 *    res.ftable( column_number ) -> Fixnum
 *
 * Returns the Oid of the table from which the column _column_number_
 * was fetched.
 *
 * Raises ArgumentError if _column_number_ is out of range or if
 * the Oid is undefined for that column.
 */
static VALUE
pgresult_ftable(VALUE self, VALUE column_number)
{
        Oid n = PQftable(get_pgresult(self), NUM2INT(column_number));
        if (n == InvalidOid) {
                rb_raise(rb_eArgError,"Oid is undefined for column: %d", 
                        NUM2INT(column_number));
        }
        return INT2FIX(n);
}